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Discussion Starter · #1 ·
My dad owned an '82 CB450SC which he bought new and sold sometime when I was around 3. Apparently he couldn't keep me off the bike and my mom was worried I'd get hurt. I've now been riding for about 5 years (SV650 then VFR800) and decided it was time to start a project with my dad to get his bike back... found an '82 Nighthawk 450 in the same color as his and in good, but not great condition and surprised him with it for Christmas. We've been working to slowly bring it back to what he remembers his bike looking like (nearly new condition) and have so far done:
Oil change
Air filter
new OEM handlebar bracket (the original had been badly damaged from keys)
new OEM fork brace cover (original had lost a lot of paint over the years)
found a good condition original seat
carb rebuild (idle was just not working, and when we pulled the carbs and cleaned it was obvious why... idle jet was filled with crud)
and here's where my problems began...

When we put the carbs back on, we tried to start the bike and found that although it would reliably start (but not idle) before pulling the carbs, now the headlight will dim and the engine won't even start to crank over. I'm guessing this is an electric problem but I'm not familiar with these bikes and I'm honestly fairly new to working on motorcycles at all. Any suggestions of where to start troubleshooting would be really appreciated!

Thanks in advance for anything you can offer to help!
 

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The start button is supposed to disconnect the headlight and energize the starter relay.
Sounds like that's a good place to start looking.
 

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Discussion Starter · #3 ·
Thanks! Going to verify that the headlight shuts off entirely when the bike tries to start. Is there a good way to check that the starter is getting power?
 

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Thanks! Going to verify that the headlight shuts off entirely when the bike tries to start. Is there a good way to check that the starter is getting power?
First thing, make sure your battery is fully charged, thats where I start. There is a solanoid between the starter and positive battery terminal. That should click when energised regardless of the starter kicking over. When the battery does not have enough power to kick over the starter you should hear a click from the solanoid. Sounds to me like you need to charge that battery.
 

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Discussion Starter · #5 ·
I was suspicious of the battery before even posting, it was old, but tried giving it a full charge and no luck. Replaced and charged a new battery, and still the same thing. Is there a list of a few tests I could try to start to run though on the starting system itself? I'd heard there was some way to jump the starter by bridging something, but not sure where I do this.
 

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Bad starter switch..... You can bridge the two "bolt" solenoid terminals to crank the engine over.....

OR, you can run a momentary jumper from battery positive to the Yellow/red stripe wire by touching it to the bolt terminal that connects to the battery....

You may phone for guidance as you do this if needed...540-525-5199....Steve
 

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Discussion Starter · #9 ·
Ug. Managed to get it to turn over (the wire to the starter switch apparently had some sort of short/missing connection). After wiggling it a little, the starter kicks over when the button is pressed.

How do we prime the carbs? Now that they're clean, I don't see a way to feed them with fuel (they're vacuum fed, right?).
 

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The carbs are gravity fed from the tank. Just turn the petcock on and wait a few minutes for all the passages to fill. Some bikes seem to need to run a few minutes to get all the air out of the passages before they smooth out.
 
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